Graphics application program interfaces (API's) have been instrumental in allowing applications to be written to a standard interface and to be run on multiple platforms, i.e. operating systems, hardware implementations, etc. Examples of such graphics API's include Open Graphics Library (OpenGL®) and Direct3D™ transform and lighting pipelines. OpenGL® is the computer industry's cross-platform standard graphics API for defining 2-D and 3-D graphic images. With OpenGL®, an application can create the same effects in any operating system using any OpenGL®-adhering graphics adapter. OpenGL® specifies a set of commands or immediately executed functions. The set of commands directs a drawing action and/or control subsequent drawing actions.
Thus, in any computer system which supports this OpenGL® standard, the operating system(s) and application software programs can make calls according to the standard, without knowing exactly any specifics regarding the hardware configuration of the system. This is accomplished by providing a complete library of low-level graphics manipulation commands, which can be used to implement graphics operations.
A significant benefit is afforded by providing a predefined set of commands in graphics API's such as OpenGL®. By restricting the allowable operations, such commands can be highly optimized in the driver and hardware implementing the graphics API. On the other hand, one major drawback of this approach is that changes to the graphics API are difficult and slow to be implemented. It may take years for a new feature to be broadly adopted across multiple vendors.
With the impending integration of transform operations into high speed graphics chips and the higher integration levels allowed by semiconductor manufacturing, it is now possible to make a significant portion of the geometry pipeline accessible to the application writer. There is thus a need to exploit this trend in order to afford increased flexibility in visual effects and computer graphics programming capabilities.